This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Previous results from several laboratories have indicated that the pp65 segament protein from CMV is the major immunogenic protein recognized by individuals who are seropositive for the virus. CTL clones, which recognize pp65 in the context of ten different HLA Class I alleles, have been identified by our laboratory. The repertoire of epitopes that have been defined for these clones are representative of approximately 95% of the ethnic population of the United States. Evaluation of whether these CTL epitopes are predominantly used in the general population requires an analysis of the immunogenecity of the approach of stimulating peripheral blood lymphocytes from HLA-typed individuals who are seropositive for CMV, in a technique in which the free peptide epitope is added at a high concentration to PBMC in microwell cultures. We have used this approach with CTL epitopes specific for pp65 and restricted by HLA A*0201, A*1101,A*2402,A*6901 and B*0702. In each case, we have examined less than five healthy volunteers who are seropositive and have been shown to respond to the CTL epitopes that are specific for the HLA allele, which they express. CD8+CTL, which recognize both peptide loaded and CMV infected targets, are amplified 100-fold in a two-week period. The use of the in vitro stimulation procedure allows a sensitive determination of whether an individual is making a CTL response to CMV, and whether pp65 is a component of that response. We wish to demonstrate that at least five, and if possible, ten randomly chosen individuals will respond to a single epitope, suggesting the potential for a universal response to that epitope from ll individuals who express the same restricting Class I allele. This provides the rationale for an approach to producing vaccine molecules, containing one or more of these epitopes to immunize at-risk individuals against CMV infection. The clinical procedures of obtaining both peripheral blood and biopsy are the central part of the clinical protocol and could be best carried out under the auspices of the GCRC. We have developed cohorts of individuals who express the HLA alleles for which we have epitopes from pp65, and more recently, pp150. We wish to carry out these studies, to characterize all of the major epitopes of CMV pp65 and pp150, which are important in the human immune response to the virus. The purpose for carrying on these studies is to define a peptide-based vaccine that would be applicable to all at-risk individuals. We will also continue to derive new CMV epitopes, to complete our repertoire of epitopes that would ensure as complete a representation as possible of individuals of different ethnicities that make up the American population. There are several consent forms (A-D) which are active for the protocol.